In 1978 to 1979 during a large urban outbreak in which 100,000 people were exposed to the fungus in Indianapolis,[7] victims had pericarditis, rheumatological syndromes, esophageal and vocal cord ulcers, parotitis, adrenal insufficiency, uveitis, fibrosing mediastinitis, interstitial nephritis, intestinal lymphangiectasia, and epididymitis.

[12] Presumed ocular histoplasmosis syndrome causes chorioretinitis, where the choroid and retina of the eyes are scarred, resulting in a loss of vision not unlike macular degeneration.

These include recurrent pneumonia, respiratory failure, fibrosing mediastinitis, superior vena cava syndrome, pulmonary vessel obstruction, and progressive fibrosis of lymph nodes.

Smokers with structural lung disease have higher probability of developing chronic cavitary histoplasmosis.

[citation needed] After healing of lesions, hard, calcified lymph nodes can erode the walls of the airway, causing hemoptysis.

The fungus has been found in poultry-house litter, caves, areas harboring bats, and bird roosts (particularly those of starlings).

The fungus is thermally dimorphic; in the environment, it grows as a brownish mycelium, and at body temperature (37 °C in humans), it morphs into a yeast.

If the patient has strong cellular immunity, macrophages, epithelial cells, and lymphocytes surround the organisms and contain them, and eventually calcify.

[21] Histoplasmosis can be diagnosed by samples containing the fungus taken from sputum (via bronchoalveolar lavage), blood, or infected organs.

It can also be diagnosed by detection of antigens in blood or urine samples by ELISA or polymerase chain reaction.

Cutaneous manifestations of disseminated disease are diverse and often present as a nondescript rash with systemic complaints.

[citation needed] The US National Institute for Occupational Safety and Health provides information on work practices and personal protective equipment that may reduce the risk of infection.

Positive histoplasmin skin tests occur in as many as 90% of the people living in areas where H. capsulatum is common, such as the eastern and central United States.

[4] In Canada, the St. Lawrence River Valley is the site of the most frequent infections, with 20–30% of the population testing positive.

[31] A review of reported cases in 2018 showed disease presence throughout Southeast Asia,[32] In India, the Gangetic West Bengal is the site of most frequent infections, with 9.4% of the population testing positive.

Workers in a variety of fields can be exposed to the fungus as spores can be released into the air through any activities which disturb soil.

[37] Due to this, occupations at a higher risk for exposure include construction and demolition, landscaping, mining, quarrying, oil and gas extraction, agriculture and forestry industries.

[37] They recommend that any build up of bird and bat droppings should be avoided if possible, but if it is unpreventable various engineering, administrative controls and personal protective equipment can be implemented in the workplace.

[40] The CDC also suggests that workplaces should be responsible for administrative controls such as developing a safety plan, posting notice of the risk of exposure, disposing of any potentially contaminated materials, and providing proper education on the dangers associated with histoplasma.